Antiwear Composition and Method of Lubricating an Internal Combustion Engine

ABSTRACT

The present invention relates to a lubricating composition containing an oil of lubricating viscosity and an antiwear package. The antiwear package may contain a derivative of a hydroxycarboxylic acid; and a salt of a sulphur-free phosphorus-containing compound. The salt includes amine salts, ammonium salts, metal salts and mixtures thereof. The invention further provides for a method of supplying an internal combustion engine with the lubricating composition.

FIELD OF INVENTION

The invention provides a lubricating composition containing an antiwear package. The invention further relates to a method of lubricating an internal combustion engine by lubricating the engine with the lubricating composition.

BACKGROUND OF THE INVENTION

Engine manufacturers have focused on improving engine design in order to improve fuel economy and efficiency (typically, based on Federal Corporate Average Fuel Economy (CAFE) standards) and reduce wear. Whilst improvements in engine design and operation have contributed, improved formulation of engine oil lubricant may also reduce wear whilst improving fuel economy and efficiency. They also serve to reduce the friction between sliding moving parts (typically metallic or ceramic) that are in contact.

It is well known for lubricating oils to contain a number of additives (including antiwear agents, antioxidants, dispersants, or detergents) used to protect internal combustion engines from wear, oxidation, soot deposits and acid build up. A common antiwear additive for engine lubricating oils is zinc dialkyldithiophosphate (ZDDP). It is believed that ZDDP antiwear additives protect the engine by forming a protective film on metal surfaces. ZDDP is also believed to have a detrimental impact on fuel economy and efficiency. Consequently, engine lubricants may also contain a friction modifier to obviate the detrimental impact of ZDDP on fuel economy and efficiency. Both ZDDP and friction modifier function by adsorption on sliding surfaces, and each may interfere with each other's respective functions.

Further, engine lubricants containing phosphorus compounds and sulphur have been shown to contribute in part to particulate emissions and emissions of other pollutants. In addition, sulphur and phosphorus tend to poison the catalysts used in catalytic converters, resulting in a reduction in performance of said catalysts.

With increasing control of emissions (often associated with contributing to NO_(x) formation, SO_(x) formation, formation of sulphated ash and reducing the efficiency of after-treatment catalytic converters) there is a desire towards reduced amounts of sulphur, phosphorus and sulphated ash in engine oils. The phosphorus from ZDDP is also believed to be relatively volatile and with the coming introduction of the GF-5 specification, tighter limits on emissions of phosphorus may be required. However, reducing the levels of antiwear additives such as ZDDP is likely to increase wear and result in other detrimental performance of an engine.

In addition, as technology develops, components of an engine are exposed to more severe operating conditions. Operating conditions may include higher power density engines, use of turbo chargers, use of alternative fuels and the like. Under many severe operating conditions, wear and/or oxidation of lubricant and components occurs more readily.

U.S. Pat. No. 5,338,470 discloses alkylated citric acid derivatives obtained as a reaction product of citric acid and an alkyl alcohol or amine. The alkylated citric acid derivative is effective as an antiwear agent and friction modifier.

U.S. Pat. No. 4,237,022 discloses tartrimides useful as additives in lubricants and fuels for effective reduction in squeal and friction as well as improvement in fuel economy.

U.S. Pat. No. 4,952,328 discloses lubricating oil compositions for internal combustion engines, comprising (A) oil of lubricating viscosity, (B) a carboxylic derivative produced by reacting a succinic acylating agent with certain amines, and (C) a basic alkali metal salt of sulphonic or carboxylic acid.

U.S. Pat. No. 4,326,972 discloses lubricant compositions for improving fuel economy of internal combustion engines. The composition includes a specific sulphurised composition (based on an ester of a carboxylic acid) and a basic alkali metal sulphonate.

U.S. Patent Application 60/862,534 (PCT/US07/082057; now US 2010-0048437) discloses malonate esters suitable as antiwear agents.

International Publication WO 2005/087904 discloses lubricants containing hydroxy carboxylic acid and hydroxy polycarboxylic acid esters in combination with phosphorus-containing additives. The phosphorus-containing additives include zinc dihydrocarbyldithiophosphates and/or neutral phosphorus compounds, such as trilauryl phosphate or triphenylphosphorothionate. The lubricants are useful in engine lubricants.

International Publication WO 2006/044411 discloses a low-sulphur, low-phosphorus, low-ash lubricant composition containing a tartrate ester, or amide having 1 to 150 carbon atoms per ester of amide group. The lubricant composition is suitable for lubricating an internal combustion engine. WO 2006/044411 does not disclose compositions as disclosed herein.

SUMMARY OF THE INVENTION

The inventors of the this invention have discovered that a lubricating composition and method as disclosed herein is capable of providing acceptable levels of at least one of (i) phosphorus emissions (typically reducing or preventing emissions), (ii) sulphur emissions (typically reducing or preventing emissions), (iii) friction performance, and (iv) wear and/or extreme pressure performance (typically reducing or preventing).

In one embodiment the invention provides a lubricating composition comprising an oil of lubricating viscosity and an antiwear package, wherein the antiwear package comprises:

-   -   (a) a derivative of a hydroxycarboxylic acid; and     -   (b) a salt of a sulphur-free phosphorus-containing compound. The         salt includes amine salts, ammonium salts, metal salts and         mixtures thereof. (“ammonium salts” include mono-, di-, tri-, or         tetraalkyl ammonium salts as well as unsubstituted ammonium         salts.)

In one embodiment the antiwear package may allow for a reduction or elimination in the amount of zinc dialkyldithiophosphate antiwear additives.

In one embodiment the invention provides a lubricating composition comprising an oil of lubricating viscosity and an antiwear package, wherein the antiwear package comprises:

-   -   (a) an antiwear agent which may be represented by a compound of         Formula (1a) and/or (1b):

wherein

n′ is 0 to 10 for Formula (1b), and 1 to 10 for Formula (1a);

p is 1 to 5;

Y and Y′ are independently —O—, >NH, >NR³, or an imide group formed by taking together both Y and Y′ groups in (1b) or two Y groups in (1a) and forming a R¹—N< group between two >C═O groups;

X is independently —CH₂—, >CHR⁴ or >CR⁴R⁵, >CHOR⁶, or >C(CO₂R⁶)₂, —CH₃, —CH₂R⁴ or —CHR⁴R⁵, —CH₂OR⁶, —CH(CO₂R⁶)₂, >C(OR₆)CO₂R⁶, >CHCO₂R⁶, or ≡C—R⁶ (where ≡ equals three valences, and may only apply to Formula (1a)) or mixtures thereof to fulfill the valence of Formula (1a) and/or (1b) (typically the compound of Formula (1a) or (1b) has at least one X that is hydroxyl-containing (e.g., >CHOR⁶, wherein R⁶ is hydrogen));

R¹ and R² are independently hydrocarbyl groups, typically containing 1 to 150, 4 to 30, or 6 to 24 carbon atoms;

R³ is a hydrocarbyl group;

R⁴ and R⁵ are independently keto-containing groups (such as acyl groups), ester groups or hydrocarbyl groups; and

R⁶ is independently hydrogen or a hydrocarbyl group, typically containing 1 to 150 carbon atoms; and

-   -   (b) a salt of a sulphur-free phosphorus-containing compound         (that is typically oil-soluble). The salt includes amine salts,         ammonium salts, metal salts and mixtures thereof.

The compound of Formula (1a) and/or (1b) may also be represented by the formula:

wherein

-   n and m may be independently integers of 1 to 5; -   X may be an aliphatic or alicyclic group, or an aliphatic or     alicyclic group containing an oxygen atom in the carbon chain, or a     substituted group of the foregoing types, said group containing up     to 6 carbon atoms and having n+m available points of attachment; -   each Y may be independently —O—, >NH, or >NR¹ or two Ys together     representing the nitrogen of an imide structure R—N<formed between     two carbonyl groups; and -   each R and R¹ may be independently hydrogen or a hydrocarbyl group,     provided that at least one R or R¹ group is a hydrocarbyl group;     each R² may be independently hydrogen, a hydrocarbyl group or an     acyl group, further provided that at least one —OR² group is located     on a carbon atom within X that is α or β to at least one of the     —C(O)—Y—R groups.

The compound derived from the hydroxy-carboxylic acid may be derived from glycolic acid (n and m both equal 1), malic acid (n=2, m=1), tartaric acid (n and m both equal 2), citric acid (n=3, m=1), or mixtures thereof. In one embodiment the compound derived from the hydroxy-carboxylic acid may be derived from tartaric acid or glycolic acid, (typically tartaric acid).

In one embodiment the derivative of hydroxycarboxylic acid includes imide, di-ester, di-amide, or ester-amide derivatives of tartaric acid, citric acid, or mixtures thereof. In one embodiment the derivative of hydroxycarboxylic acid includes an imide, a di-ester, a di-amide, or an ester-amide derivative of tartaric acid.

When X is hydroxyl-containing, the compound Formula (1a) and/or (1b) may be derived from hydroxycarboxylic acids such as tartaric acid, citric acid, or mixtures thereof. In one embodiment the compound Formula (1a) and/or (1b) is derived from citric acid and R¹ and R² contain at least 6 or at least 8 carbon atoms up to 150, or 6 to 30, or 8 to 24 carbon atoms. In one embodiment the compound Formula (1a) and/or (1b) is derived from tartaric acid and R¹ and R² contain 4 to 30, or 6 to 24 carbon atoms.

When X is not hydroxyl-containing, the compound Formula (1a) and/or (1b) may be derived from, e.g., malonic acid, oxalic acid, chlorophenyl malonic acid, or mixtures thereof.

In different embodiments component (b) of the lubricating composition may be a salt of a sulphur-free phosphorus-containing compound selected from the group consisting of sulphur-free metal salts of hydrocarbyl-substituted phosphorus-containing compounds and phosphorylated dispersants.

In different embodiments the lubricating compositions disclosed herein contain 0 ppm to 1000 ppm, 0 ppm to 500 ppm, or 5 ppm to 300 ppm, or 20 ppm to 250 ppm of molybdenum.

In one embodiment the invention provides a method for lubricating an internal combustion engine comprising supplying to the engine a lubricating composition as disclosed herein.

In different embodiments the lubricating composition defined for the method contains the salt of a sulphur-free phosphorus-containing compound which may be selected from the group consisting of a sulphur-free metal salt of a hydrocarbyl-substituted phosphorus-containing compound, a phosphorylated dispersant, a hydroxy-substituted di-ester of phosphoric acid, a phosphorylated hydroxy-substituted di- or tri-ester of phosphoric acid or salt, and mixtures thereof.

In one embodiment the invention provides for the use of a lubricating composition as disclosed herein for providing acceptable levels of at least one of (i) phosphorus emissions (typically reducing or preventing emissions), (ii) sulphur emissions (typically reducing or preventing emissions), (iii) friction performance, and (iv) wear and/or extreme pressure performance (typically reducing or preventing).

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a lubricating composition and a method for lubricating a mechanical device as disclosed above. Typically the mechanical device is an internal combustion engine.

Antiwear Package

The antiwear package includes two or more antiwear agents as disclosed above.

The antiwear package may be present at 0.01 wt % to 10 wt %, or 0.05 wt % to 10 wt %, or 0.05 wt % to 5 wt % of the lubricating composition.

The derivative of a hydroxycarboxylic acid (or the antiwear agent represented by a compound of Formula (1a) and/or (1b)) may be present at 0.005 wt % to 10 wt %, or 0.025 to 5 wt %, or 0.25 to 2.5 wt % of the lubricating composition.

Antiwear Agent Represented by a Compound of Formula (1a) and/or (1b))

In one embodiment the antiwear agent represented by a compound of Formula (1a) and/or (1b) may be a derivative of a hydroxycarboxylic acid.

In one embodiment one antiwear agent includes a derivative of a hydroxycarboxylic acid. The derivative of a hydroxycarboxylic acid, typically a tartrate, may also function as rust and corrosion inhibitor, friction modifier, antiwear agent and demulsifier. In one embodiment the derivative of a hydroxycarboxylic acid may also have friction modifying properties.

In one embodiment the derivative of a hydroxycarboxylic acid may be ashless (i.e., does not contain metal in amounts greater than those associated with contaminant amounts).

Derivatives of the hydroxycarboxylic acid include imides, di-esters, di-amides, di-imides (applicable for tetra-acids and higher), ester-amides, ester-imides (applicable for tri-acids and higher, such as citric acid), or imide-amides (applicable for tri-acids and higher, such as citric acid). In one embodiment the antiwear agent includes imides, di-esters, di-amides, or ester-amides.

In one embodiment the antiwear agent may be derived from at least one of a hydroxy-carboxylic acid di-ester, a hydroxy-carboxylic acid di-amide, a hydroxy-carboxylic acid di-imide (applicable for tetra-acids and higher), a hydroxy-carboxylic acid ester-amide, a hydroxy-carboxylic acid ester-imide (applicable for tri-acids and higher, such as citric acid), and a hydroxy-carboxylic acid imide-amide (applicable for tri-acids and higher, such as citric acid). In one embodiment the antiwear agent may be derived from at least one of the group consisting of a hydroxy-carboxylic acid di-ester, a hydroxy-carboxylic acid di-amide, and a hydroxy-carboxylic acid ester-amide.

Examples of a suitable a hydroxycarboxylic acid include citric acid, tartaric acid, malic acid (or hydroxy-succinic acid), mandelic acid, lactic acid, glycolic acid, hydroxy-propionic acid, hydroxyglutaric acid, or mixtures thereof. In one embodiment the antiwear agent may be derived from tartaric acid, citric acid, hydroxy-succinic acid, dihydroxy mono-acids, mono-hydroxy diacids, or mixtures thereof. In one embodiment the antiwear agent includes a compound derived from tartaric acid.

US Patent Application 2005/198894 discloses suitable hydroxycarboxylic acid compounds, and methods of preparing the same.

Canadian Patent 1183125; US Patent Publication numbers 2006/0183647 and US-2006-0079413; U.S. Patent Application No. 60/867,402 (PCT/US07/085547); and British Patent 2 105 743 A, all disclose examples of suitable tartaric acid derivatives.

A detailed description of methods for preparing suitable tartrimides (by reacting tartaric acid with a primary amine) is disclosed in U.S. Pat. No. 4,237,022.

In one embodiment the antiwear agent includes imide, di-esters, di-amides, ester-amide derivatives of tartaric acid.

In one embodiment the antiwear agent may be represented by a compound of Formula (1a) and/or (1b) as defined above:

wherein

n′ is 0 to 10, 0 to 6, or 0 to 4 for Formula (1b), and for Formula (1a) 1 to 4, or 1 to 2;

p is 1 to 5, or 1 to 2, or 1;

Y and Y′ are independently —O—, >NH, >NR³, or an imide group formed by taking together both Y and Y′ groups and forming a R¹—N< group between two >C═O groups;

X is independently —CH₂—, >CHR⁴ or >CR⁴R⁵, >CHOR⁶, or >C(CO₂R⁶)₂, —CH₃, —CH₂R⁴ or CHR⁴R⁵, —CH₂OR⁶, —CH(CO₂R⁶)₂, >C(OR₆)CO₂R⁶, >CHCO₂R⁶, or ≡C—R⁶ (where ≡ equals three valences, and may only apply to Formula (1a)) or mixtures thereof to fulfill the valence of Formula (1a) and/or (1b) (typically the compound of Formula (1a) or (1b) has at least one X that is hydroxyl-containing (i.e., >CHOR⁶, wherein R⁶ is hydrogen));

R¹ and R² are independently hydrocarbyl groups, typically containing 1 to 150, 4 to 30, or 6 to 20, or 10 to 20, or 11 to 18 carbon atoms;

R³ is a hydrocarbyl group;

R⁴ and R⁵ are independently keto-groups, ester groups or hydrocarbyl groups; and

R⁶ is independently hydrogen or a hydrocarbyl group, typically containing 1 to 150, or 4 to 30 carbon atoms.

In one embodiment the di-esters, di-amides, di-imides (applicable for tetra-acids and higher), ester-amide, ester-imide (applicable for tri-acids and higher, such as citric acid), imide-amide (applicable for tri-acids and higher, such as citric acid) compounds may be derived from a compound of Formula (1a) and/or (1b). In one embodiment the di-esters, di-amides, ester-amide, compounds may be derived from a compound of Formula (1a) and/or (1b).

In one embodiment the compound of Formula (1b) contains an imide group. The imide group is typically formed by taking together the Y and Y′ groups in (1b) or alternatively in Formula (1a), two Y groups, and forming a R¹—N< group between two >C═O groups.

In one embodiment the compound of Formula (1a) and/or (1b) has n, X, and R¹, R² and R⁶ defined as follows: n is 1 to 2, X is >CHOR⁶; and R¹ and R² are independently hydrocarbyl groups containing 4 to 30 carbon atoms, and R⁶ is independently hydrogen or a hydrocarbyl group containing 4 to 30 carbon atoms.

In one embodiment Y and Y′ are both —O—.

In one embodiment the compound of Formula (1a) and/or (1b) has n, X, Y, Y′ and R¹, R² and R⁶ defined as follows: n is 1 to 2, X is >CHOR⁶; Y and Y′ are both —O—, and R¹ and R² are independently hydrocarbyl groups containing 4 to 30 carbon atoms, and R⁶ is independently hydrogen or a hydrocarbyl group containing 4 to 30 carbon atoms.

The di-esters, di-amides, di-imides (applicable for tetra-acids and higher), ester-amide, ester-imide (applicable for tri-acids and higher, such as citric acid), imide-amide (applicable for tri-acids and higher, such as citric acid) compounds of Formula (1a) and/or (1b) may be prepared by reacting a polycarboxylic acid (such as tartaric acid), with an amine or alcohol, optionally in the presence of a known esterification catalyst. The amine or alcohol typically has sufficient carbon atoms to fulfill the requirements of R¹ and/or R² as defined in Formula (1a) and/or (1b).

In one embodiment R¹ and R² may be independently linear or branched hydrocarbyl groups. In one embodiment the hydrocarbyl groups may be branched. In one embodiment the hydrocarbyl groups may be linear. The R¹ and R² may be incorporated into Formula (1a) and/or (1b) by either an amine or an alcohol. The alcohol includes both monohydric alcohol and polyhydric alcohol. In one embodiment the alcohol is branched.

In one embodiment the antiwear agent may be derived from a compound of Formula (1b).

Examples of a suitable branched alcohol include 2-ethylhexanol, isotridecanol, Guerbet alcohols, or mixtures thereof.

Examples of a monohydric alcohol include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, nonadecanol, eicosanol, or mixtures thereof. In one embodiment the monohydric alcohol contains 5 to 20 carbon atoms.

The alcohol includes either a monohydric alcohol or a polyhydric alcohol. Examples of a suitable polyhydric alcohol include ethylene glycol, propylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 1,5-pentane diol, 1,6-hexane diol, glycerol, sorbitol, pentaerythritol, trimethylolpropane, starch, glucose, sucrose, methylglucoside, or mixtures thereof. In one embodiment the polyhydric alcohol may be used in a mixture along with a monohydric alcohol. Typically, in such a combination the monohydric alcohol constitutes at least 60 mole percent, or at least 90 mole percent of the mixture.

In one embodiment the antiwear agent may be derived from tartaric acid. The tartaric acid used for preparing the tartrates of the invention may be commercially available (for instance, obtained from Sargent Welch), and it is likely to exist in one or more isomeric forms such as d-tartaric acid, 1-tartaric acid, d,1-tartaric acid (racemic mixture) or mesotartaric acid, often depending on the source (natural) or method of synthesis (e.g., from maleic acid). These derivatives may also be prepared from functional equivalents to the diacid readily apparent to those skilled in the art, such as esters, acid chlorides, or anhydrides.

When the compound of Formula (1a) and/or (1b) is derived from tartaric acid, resultant tartrates may be solid, semi-solid, or oil depending on the particular alcohol used in preparing the tartrate. For use as additives in oleaginous compositions including lubricating and fuel compositions the tartrates are advantageously soluble and/or stably dispersible in such oleaginous compositions. For example, compositions intended for use in oils are typically oil-soluble and/or stably dispersible in an oil in which they are to be used. The term “oil-soluble” as used in this specification and appended claims does not necessarily mean that all the compositions in question are miscible or soluble in all proportions in all oils. Rather, it is intended to mean that the composition is soluble in an oil (e.g., mineral oil, or synthetic oil) in which it is intended to function to an extent which permits the solution to exhibit one or more of the desired properties. Similarly, it is not necessary that such “solutions” be true solutions in the strict physical or chemical sense. They may instead be micro-emulsions or colloidal dispersions which, for the purpose of this invention, exhibit properties sufficiently close to those of true solutions to be, for practical purposes, interchangeable with them within the context of this invention.

Salt of a Sulphur-Free Phosphorus-Containing Compound

The salt of a sulphur-free phosphorus-containing compound may be selected from the group consisting of a sulphur-free metal or amine salt of a hydrocarbyl-substituted phosphorus-containing compound, a phosphorylated dispersant, a hydroxy-substituted di-ester of phosphoric acid, a phosphorylated hydroxy-substituted di- or tri-ester of phosphoric acid, and mixtures thereof.

Amine Salt of Phosphorus-Containing Compound

In one embodiment an amine salt of a sulphur-free phosphorus-containing compound may be a salt of either (i) a hydroxy-substituted di-ester of phosphoric acid, or (ii) a phosphorylated hydroxy-substituted di- or tri-ester of phosphoric acid. The amine salt of a sulphur-free phosphorus-containing compound may be represented Formula (2):

wherein

A and A′ are independently H, or a hydrocarbyl group containing 1 to 30 carbon atoms;

each R and R″ group are independently a hydrocarbyl group;

each R′ is independently R, H, or a hydroxyalkyl group;

Y is independently R′, or a group represented by RO(R′O)P(O)—CH(A′)CH(A)- (such as RO(R′O)P(O)—CH₂CH(CH₃)—);

x′ ranges from 0 to 1 (in one embodiment when x′=0, R′ is a hydroxyalkyl group); and

m and n are both positive non-zero integers, with the proviso that the sum of (m+n) is equal to 4;

M is a metal ion;

t is an integer varying from 1 to 4 (or 1 to 2); and

q and e are fractions, whose total provides complete valence to satisfy t, with the proviso that q is in the range of 0.1 to 1.5 (or 0.1 to 1), and e is in the range of 0 to 0.9.

The amine salt of a sulphur-free phosphorus-containing compound may be represented by Formula (2a):

wherein

A and A′ are independently H, or a hydrocarbyl group containing 1 to 30 carbon atoms;

each R and R″ group are independently a hydrocarbyl group;

each R′ is independently R, H, or a hydroxyalkyl group;

Y is independently R′, or a group represented by RO(R′O)P(O)—CH(A′)CH(A)- (such as RO(R′O)P(O)—CH₂CH(CH₃)—);

x′ ranges from 0 to 1 (in one embodiment when x′=0, R′ is a hydroxyalkyl group);

m and n are both positive non-zero integers, with the proviso that the sum of (m+n) is equal to 4.

In one embodiment the compound represented by Formula (2) or Formula (2a) has x′ equal to 1.

In one embodiment the compound represented by Formula (2) or Formula (2a) has x′ is equal to 0.

In one embodiment the compound represented by Formula (2) or Formula (2a) has m equal to 2; and n equal to 2.

In one embodiment the compound represented by Formula (2) or Formula (2a) has m equal to 3; and n equal to 1.

In one embodiment A and A′ independently contain 1 to 10, or 2 to 6, or 2 to 4 carbon atoms.

In one embodiment R, R′ and R″ all independently contain 1 to 30, or 1 to 20, or 4 to 20 carbon atoms. In one embodiment up to half of the R′ groups may be hydrogen.

In one embodiment R″ contains 8 to 26, or 10 to 20, or 13 to 19 carbon atoms.

In one embodiment when x′ is equal to 0, the compound of Formula (2) or Formula (2a) may be an amine phosphate as disclosed in U.S. Pat. No. 6,468,946. The amine phosphate disclosed therein may be a mono- or di-hydrocarbyl-substituted ester of a phosphorus compound salted with an amine.

Each hydrocarbyl-substituted ester group may contain 4 to 40 or 6 to 20 carbon atoms.

Examples of suitable compounds are also disclosed in Examples P-4 to P-8 of U.S. Pat. No. 6,468,946 (see paragraphs [0060] to [0064]). The reactions described in P-4 to P-8 of U.S. Pat. No. 6,468,946 may also be repeated with other alcohols, including saturated or unsaturated alcohols containing 12 to 15, or 16 to 18 or 20 to 24 carbon atoms. A useful alcohol is a C₁₈ alcohol.

The compound of Formula (2) or Formula (2a) includes amine salts of a primary amine, a secondary amine, a tertiary amine, or mixtures thereof. In one embodiment the primary amine includes a tertiary-aliphatic primary amine.

Examples of suitable primary amines include ethylamine, propylamine, butylamine, 2-ethylhexylamine, octylamine, and dodecylamine, as well as such fatty amines as n-octylamine, n-decylamine, n-dodecylamine, n-tetradecylamine, n-hexadecylamine, n-octadecylamine and oleyamine. Other useful fatty amines include commercially available fatty amines such as “Armeen®” amines (products available from Akzo Chemicals, Chicago, Ill.), such as Armeen C, Armeen O, Armeen O L, Armeen T, Armeen H T, Armeen S and Armeen S D, wherein the letter designation relates to the fatty group, such as coco, oleyl, tallow, or stearyl groups.

Examples of suitable secondary amines include dimethylamine, diethylamine, dipropylamine, dibutylamine, diamylamine, dihexylamine, diheptylamine, methylethylamine, ethylbutylamine, bis-2-ethylhexylamine, N-methyl-1-amino-cyclohexane, Armeen® 2C and ethylamylamine. The secondary amines may be cyclic amines such as piperidine, piperazine and morpholine.

Examples of tertiary amines include tri-n-butylamine, tri-n-octylamine, tri-decylamine, tri-laurylamine, tri-hexadecylamine, tri-2-ethylhexyl amine, and dimethyloleylamine (Armeen® DMOD).

In one embodiment the amines may be in the form of a mixture. Examples of suitable mixtures of amines include (i) an amine with 11 to 14 carbon atoms on tertiary alkyl primary groups, (ii) an amine with 14 to 18 carbon atoms on tertiary alkyl primary groups, or (iii) an amine with 18 to 22 carbon atoms on tertiary alkyl primary groups. Other examples of tertiary alkyl primary amines include tert-butylamine, tert-hexylamine, tert-octylamine (such as 1,1-dimethylhexylamine), tert-decylamine (such as 1,1-dimethyloctylamine), tertdodecylamine, tert-tetradecylamine, tert-hexadecylamine, tert-octadecylamine, tert-tetracosanylamine, and tert-octacosanylamine.

In one embodiment a useful mixture of amines includes “Primene® 81R” or “Primene® JMT.” Primene® 81R and Primene® JMT (both produced and sold by Rohm & Haas) may be mixtures of C11 to C14 tertiary alkyl primary amines and C18 to C22 tertiary alkyl primary amines respectively.

In one embodiment the metal ion of Formula (2) may be a mono- or di-valent metal, or mixtures thereof. In one embodiment the metal ion may be divalent.

In one embodiment the metal of the metal ion includes lithium, sodium, potassium, calcium, magnesium, barium, copper, nickel, tin or zinc.

In one embodiment the metal of the metal ion includes lithium, sodium, calcium, magnesium, or zinc. In one embodiment the metal of the metal ion may be zinc.

In one embodiment t is equal to 1, when the compound of Formula (2) is an amine salt or a metal salt of a monovalent metal.

In one embodiment t is equal to 2, when the compound of Formula (2) is a metal salt of a divalent metal.

In one embodiment q is in the range of 0.5 to 1; and e is in the range of 0 to 0.5.

In one embodiment the compound of Formula (2) is free of a metal ion (e is equal to zero; and q is equal to one).

In one embodiment t is equal to 1, e is equal to 0, and q is equal to 1.

Processes to Prepare Compound of Formula (2) and Formula (2a)

In one embodiment the sulphur-free amine salt of a phosphorus-containing compound is obtained/obtainable by a process comprising: reacting an amine with either (i) a hydroxy-substituted di-ester of phosphoric acid, or (ii) a phosphorylated hydroxy-substituted di- or tri-ester of phosphoric acid.

In one embodiment the sulphur-free amine salt of a phosphorus-containing compound is obtained/obtainable by a process comprising: reacting an amine with either (i) a hydroxy-substituted di-ester of phosphoric acid, or (ii) a phosphorylated hydroxy-substituted di- or tri-ester of phosphoric acid.

In one embodiment the salt of a hydroxy-substituted di-ester of phosphoric acid may be prepared by a process comprising:

(i) reacting a phosphating agent (such as P₂O₅, P₄O₁₀, or equivalents thereof) with an alcohol, to form a mono- and/or di-phosphate ester;

(ii) reacting the phosphate ester with an alkylene oxide, to form a hydroxy-substituted di-ester of phosphoric acid; and

(iii) salting the hydroxy-substituted di-ester of phosphoric acid is reacted with an amine and/or metal.

In one embodiment the hydroxy-substituted di-ester of phosphoric acid of (ii) may be further reacted at least once more, by repeating step (i) above, with a phosphating agent (typically forming a phosphorylated hydroxy-substituted di- or tri-ester of phosphoric acid), before salting with an amine and/or metal (as in step (iii) above).

In different embodiments, steps (i) and (ii) may be repeated at least once more, optionally followed by step (i) before salting with an amine and/or metal (as in step (iii) above). For example the salts may be prepared by a process comprising performing the steps (i),(ii), and (iii); or (i),(ii),(i), and (iii); or (i),(ii),(i),(ii), and (iii); (i),(ii),(i),(ii),(i), and (iii), or (i),(ii),(i),(ii),(i), (ii), and (iii), or (i),(ii),(i),(ii),(i),(ii),(i) and (iii), or (i),(ii),(i),(ii),(i),(ii),(i),(ii) and (iii), as defined above.

In different embodiments the reaction product yields 1 wt % to 99 wt %, or 20 wt % to 80 wt %, or 35 wt % to 75 wt %, of the sulphur-free amine salt of a phosphorus-containing compound of the invention.

In different embodiments, the mole ratio in step (i) of the mono-phosphate to di-phosphate includes ranges of 1:10 to 10:1, or 1:5 to 5:1, or 1:2 to 2:1, or 1:1.

In different embodiments, the mole ratio (based on the amount of phosphorus) in step (i) of alkylene oxide to the mono- and/or di-phosphate ester of step (i) includes ranges of 0.6:1 to 1.5:1, or 0.8:1 to 1.2:1, including 1:1.

In one embodiment alkylene oxide includes ethylene oxide, propylene oxide or butylene oxide; the mole ratio of alkylene oxide to hydroxy-substituted di-ester of phosphoric acid in step (ii) includes 1:1.

In one embodiment alkylene oxide includes C₅ and higher alkylene oxide; and the mole ratio of alkylene oxide to the hydroxy-substituted di-ester of phosphoric acid in step (ii) includes broader ranges because the alkylene oxides are less volatile under reaction conditions.

The process described above in steps (i) to (iii), in different embodiments may be carried out at a reaction temperature in a range of 30° C. to 140° C., or 40° C. to 110° C., or 45° C. to 90° C.

The process may be carried out at reduced pressure, atmospheric pressure or above atmospheric pressure. In one embodiment the process may be carried out at atmospheric pressure or above atmospheric pressure.

In one embodiment the process may be carried out in an inert atmosphere. Examples of a suitable inert atmosphere include nitrogen, argon, or mixtures thereof.

In different embodiments, the alkylene oxide contains 2 to 10, or 2 to 6, or 2 to 4 carbon atoms. In one embodiment the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, or mixtures thereof. In one embodiment the alkylene oxide includes propylene oxide.

In different embodiments, the alcohol contains 1 to 30, or 4 to 24, or 8 to 18 carbon atoms. The alcohol may be linear or branched. The alcohol may be saturated or unsaturated.

Examples of a suitable alcohol include hexanol, heptanol, octanol, nonanol, dodecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, octadecenol (oleyl alcohol), nonadecanol, eicosyl-alcohol, or mixtures thereof. Examples of a suitable alcohol include for example, 4-methyl-2-pentanol, 2-ethylhexanol, isooctanol, or mixtures thereof.

Examples of commercially available alcohols include Oxo Alcohol® 7911, Oxo Alcohol® 7900 and Oxo Alcohol® 1100 of Monsanto; Alphanol® 79 of ICI; Nafol® 1620, Alfol® 610 and Alfol® 810 of Condea (now Sasol); Epal® 610 and Epal® 810 of Ethyl Corporation; Linevol® 79, Linevol® 911 and Dobanol® 25 L of Shell AG; Lial® 125 of Condea Augusta, Milan; Dehydad® and Lorol® of Henkel KGaA (now Cognis) as well as Linopol® 7-11 and Acropol® 91 of Ugine Kuhlmann.

Useful amines include amine salts of a primary amine, a secondary amine, a tertiary amine, or mixtures thereof. A more detailed description of useful amines is defined above.

The amine salt of a phosphoric acid may be prepared by the methodology described in International Publication WO 2008/094759. In particular Preparative Examples 1 to 4 described in paragraphs [0151 to [0158].

Sulphur-Free Metal Salt of a Hydrocarbyl-Substituted Phosphorus-Containing Compound

In one embodiment the salt of a sulphur-free phosphorus-containing compound is known and may be prepared as is disclosed in EP 287 618, U.S. Pat. No. 2,228,658, U.S. Pat. No. 4,431,552 and U.S. Pat. No. 2,310,175. Examples of the salt of sulphur-free phosphorus-containing compound disclosed therein include a metal hydrocarbyl-substituted phosphonate, a metal hydrocarbyl-substituted phosphinate, a metal hydrocarbyl-substituted phosphite, a metal hydrocarbyl-substituted phosphonite, a metal hydrocarbyl-substituted phosphinite, or mixtures thereof.

In one embodiment the phosphorus atom of the hydrocarbyl-substituted phosphorus-containing compound is pentavalent.

In one embodiment the sulphur-free metal salt of a hydrocarbyl-substituted phosphorus-containing compound is a metal hydrocarbyl-substituted phosphonate or mixtures thereof.

Phosphorylated Dispersant

In one embodiment the salt of a sulphur-free phosphorus-containing compound is a phosphorylated dispersant. The phosphorylated dispersant may be prepared by reacting an inorganic phosphorus acid or anhydride with a nitrogen-containing dispersant. The resultant phosphorylated dispersant is believed to form an amine salt of the nitrogen-containing dispersant and the counterion is derived from the phosphorylating agent. Typically the nitrogen-containing dispersant is ashless. It is desirable to ensure the reaction of the inorganic phosphorus acid or anhydride with the nitrogen-containing dispersant produces a product that incorporates the phosphorus into the dispersant instead of forming insoluble phosphorus particulates. If solid particulates form, the resultant product is likely to be hazy and less stable. The use of such a product may reduce the effects observed by the present invention.

Ashless dispersants are typically known, prior to mixing in a lubricating oil composition, not to contain ash-forming metals and they do not normally contribute any ash forming metals when added to a lubricant and polymeric dispersants. Ashless dispersants are characterised by a polar group attached to a relatively high molecular weight hydrocarbon chain.

Examples of inorganic phosphorus acids or anhydride which are useful in forming the salt of a sulphur-free phosphorus-containing compound include phosphorous acid, phosphoric acid (H₃PO₄), hypophosphoric acid, phosphorus trioxide (P2O3), phosphorus tetraoxide (P₂O₄), and phosphoric anhydride (P₂O₅, or P₄O₁₀). In one embodiment the inorganic phosphorus acids or anhydride may be either is phosphorous acid (H₃PO₃) or phosphoric acid (H₃PO₄).

The inorganic, oil-insoluble phosphorus containing acids may be reacted with the ashless dispersant which contains basic nitrogen or one or more free hydroxyl groups. The resulting product is believed to be oil-soluble. The nitrogen-containing dispersants include: (i) hydrocarbyl-substituted succinimides; (ii) mixed ester/amides of hydrocarbyl-substituted succinic acid made using alkanols, amines, and/or aminoalkanols; (iii) Mannich dispersants which are condensation products of hydrocarbyl-substituted phenols, formaldehyde and polyethylene polyamines (described in U.S. Pat. Nos. 3,368,972; 3,413,374; 3,539,633; 3,649,279; 3,798,247 and 3,803,039); and (iv) mixtures thereof.

Typical ashless dispersants include N-substituted long chain alkenyl succinimides. Examples of N-substituted long chain alkenyl succinimides include polyisobutylene succinimide with number average molecular weight of the polyisobutylene substituent in the range 350 to 5000, 500 to 3000, or 550 to 2500. Succinimide dispersants and their preparation are disclosed, for instance in U.S. Pat. No. 3,172,892 or U.S. Pat. No. 4,234,435 and in EP 0355895. Succinimide dispersants are typically the imide formed from a polyamine, typically a poly(ethyleneamine).

In one embodiment the invention further comprises at least one dispersant derived from polyisobutylene succinimide with number average molecular weight in the range 350 to 5000, 500 to 3000, or 550 to 2500. The polyisobutylene succinimide may be used alone or in combination with other dispersants.

Oils of Lubricating Viscosity

The lubricating composition comprises an oil of lubricating viscosity. Such oils include natural and synthetic oils, oil derived from hydrocracking, hydrogenation, and hydrofinishing, unrefined, refined, re-refined oils or mixtures thereof. A more detailed description of unrefined, refined and re-refined oils is provided in International Publication WO2008/147704, paragraphs [0054] to [0056]. A more detailed description of natural and synthetic lubricating oils is described in paragraphs [0058] to respectively of WO2008/147704. Synthetic oils may also be produced by Fischer-Tropsch reactions and typically may be hydroisomerised Fischer-Tropsch hydrocarbons or waxes. In one embodiment oils may be prepared by a Fischer-Tropsch gas-to-liquid synthetic procedure as well as other gas-to-liquid oils.

Oils of lubricating viscosity may also be defined as specified in April 2008 version of “Appendix E—API Base Oil Interchangeability Guidelines for Passenger Car Motor Oils and Diesel Engine Oils”, section 1.3 Sub-heading 1.3. “Base Stock Categories”. In one embodiment the oil of lubricating viscosity may be an API Group I, or Group II, or Group III, or Group IV oil. In one embodiment the oil of lubricating viscosity may be an API Group II or Group III oil.

The amount of the oil of lubricating viscosity present is typically the balance remaining after subtracting from 100 wt % the sum of the amount of the compound of the invention and the other performance additives.

The lubricating composition may be in the form of a concentrate and/or a fully formulated lubricant. If the lubricating composition of the invention (comprising the additives disclosed hereinabove) is in the form of a concentrate which may be combined with additional oil to form, in whole or in part, a finished lubricant), the ratio of the of these additives to the oil of lubricating viscosity and/or to diluent oil include the ranges of 1:99 to 99:1 by weight, or 80:20 to 10:90 by weight.

Other Performance Additives

The composition optionally comprises other performance additives. These performance additives are well known to a skilled person. The performance additives include metal deactivators, viscosity modifiers (such as hydrogenated copolymers of styrene-butadiene, ethylene-propylene copolymers, or mixtures thereof), detergents (such as salicylates, sulphonates, salixarates, phenates, or mixtures thereof), friction modifiers (such as glycerol monooleate), antiwear agents (such as zinc dialkyldithiophosphates), corrosion inhibitors, dispersants (typically succinimides), dispersant viscosity modifiers, extreme pressure agents, antioxidants (including alkylated diphenylamines (typically di-nonyl diphenylamine, octyl diphenylamine, di-octyl diphenylamine), hindered phenols, oil-soluble molybdenum compounds, or mixtures thereof), foam inhibitors, demulsifiers, pour point depressants, seal swelling agents and mixtures thereof. Typically, fully-formulated lubricating oil will contain one or more of these performance additives.

In one embodiment the lubricating composition further comprises at least one of a viscosity modifier, an antioxidant, an overbased detergent, a succinimide dispersant (other than the phosphorylated dispersant of the invention), an antiwear agent (other than those described herein as part of the invention), or mixtures thereof.

In one embodiment the lubricating composition is free of zinc dihydrocarbyl dithiophosphate. In one embodiment the lubricating composition further includes zinc dihydrocarbyl dithiophosphate.

In one embodiment a hindered phenol antioxidant is an ester and may include, e.g., Irganox™ L-135 from Ciba or an addition product derived from 2,6-di-tert-butylphenol and an alkyl acrylate, wherein the alkyl group may contain 1 to 18, or 2 to 12, or 2 to 8, or 2 to 6, or 4 carbon atoms. A more detailed description of suitable ester-containing hindered phenol antioxidant chemistry is found in U.S. Pat. No. 6,559,105.

In one embodiment the lubricating composition further contains an oil-soluble molybdenum compound. The molybdenum compound may have the functional performance of an antiwear agent, an antioxidant, a friction modifier, or mixtures thereof. Typically, the oil-soluble molybdenum compound includes molybdenum dithiocarbamates, molybdenum dialkyldithiophosphates, amine salts of molybdenum compounds, molybdenum xanthates, molybdenum sulphides, molybdenum carboxylates, molybdenum alkoxides, or mixtures thereof. The molybdenum sulphides include molybdenum disulphide. In one embodiment the oil-soluble molybdenum compound is a molybdenum dithiocarbamate.

Suitable examples of molybdenum dithiocarbamates which may be used as an antioxidant include commercial materials sold under the trade names such as Molyvan 822™ and Molyvan™ A from R.T. Vanderbilt Co., Ltd., and Adeka Sakura-Lube™ S-100, S-165, S-515, and S-600 from Asahi Denka Kogyo KK and mixtures thereof.

INDUSTRIAL APPLICATION

In one embodiment the mechanical device is an internal combustion engine.

In one embodiment the internal combustion engine may be a diesel fueled engine, a gasoline fueled engine, a natural gas fueled engine or a mixed gasoline/alcohol fueled engine. In one embodiment the internal combustion engine may be a diesel fueled engine and in another embodiment a gasoline fueled engine.

The internal combustion engine may be a 2-stroke or 4-stroke engine. Suitable internal combustion engines include marine diesel engines, aviation piston engines, low-load diesel engines, and automobile and truck engines.

In one embodiment the internal combustion engine contains components of an aluminium-alloy. The aluminium-alloy includes aluminium silicates, aluminium oxides, or other ceramic materials. In one embodiment the aluminium-alloy is an aluminium-silicate surface.

The lubricant composition for an internal combustion engine may be suitable for any engine lubricant irrespective of the sulphur, phosphorus or sulphated ash (ASTM D-874) content. The sulphur content of the engine oil lubricant may be 1 wt % or less, or 0.8 wt % or less, or 0.5 wt % or less, or 0.3 wt % or less. In one embodiment the sulphur content may be in the range of 0.001 wt % to 0.5 wt %, or 0.01 wt % to 0.3 wt %. The phosphorus content may be 0.2 wt % or less, or 0.1 wt % or less, or 0.085 wt % or less, or even 0.06 wt % or less, 0.055 wt % or less, or 0.05 wt % or less. In one embodiment the phosphorus content may be 100 ppm to 1000 ppm, or 200 ppm to 600 ppm. The total sulphated ash content may be 2 wt % or less, or 1.5 wt % or less, or 1.1 wt % or less, or 1 wt % or less, or 0.8 wt % or less, or 0.5 wt % or less. In one embodiment the sulphated ash content may be 0.05 wt % to 0.9 wt %, or 0.1 wt % to 0.2 wt % to 0.45 wt %.

In one embodiment the lubricating composition is an engine oil, wherein the lubricating composition is characterised as having (i) a sulphur content of 0.5 wt % or less, (ii) a phosphorus content of 0.07 wt % or less, and (iii) a sulphated ash content of 1.5 wt % or less.

In one embodiment the lubricating composition is suitable for a 2-stroke or a 4-stroke marine diesel internal combustion engine. In one embodiment the marine diesel combustion engine is a 2-stroke engine.

The antiwear package may contain the compound of Formula (1a) and/or (1b) (or in one embodiment the derivative of a hydroxycarboxylic acid) in an internal combustion engine lubricant at an amount in the range of 0.005 wt % to 10 wt %, or 0.025 to 5 wt %, or 0.25 to 2.5 wt % of the lubricating composition.

The antiwear package may contain the salt of a sulphur-free phosphorus-containing compound in an internal combustion engine lubricant at an amount in the range of 0.005 wt % to 10 wt %, or 0.025 to 5 wt %, or 0.25 to 2.5 wt % of the lubricating composition.

The following examples provide illustrations of the invention. These examples are non-exhaustive and are not intended to limit the scope of the invention.

EXAMPLES Preparative Comparative Example 1 (PGE1)

Amine Salt of Phosphorylated Hydroxyalkyl Ester of Thiophosphoric Acid: Phosphorus pentoxide (144 grams) is added in two portions one hour apart to 1176 grams of hydroxypropyl O,O-di(4-methyl-2-pentyl)phosphorodithioate (prepared by reacting di(4-methyl-2-pentyl)-phosphorodithioic acid with about 1.1 moles of propylene oxide at 54° C. and removing excess propylene oxide by vacuum stripping). The mixture is heated at 71° C. for 6 hours to give an acidic intermediate (1320 g). This intermediate is neutralised by adding 555 g of a C₁₂₋₁₄-alkyl amine over two hours at 49° C. After heating to 77° C. the material is vacuum stripped to give the product.

Engine Oil Lubricants (CE1 to CE4 and EX1 to EX2)

Example 1 (EX1) is an internal combustion lubricant containing (i) 0.9 wt % of an amine phosphate prepared in a similar manner to P-4 as is described in U.S. Pat. No. 6,468,946, except the alcohol employed is a C18 alcohol, (ii) a tartrate diester of a C₆ to C₁₅ alcohol, and (iii) other conventional engine oil additives including antioxidants, viscosity modifiers, succinimide dispersants, glycerol monooleate friction modifiers, foam inhibitors, pour point depressants, and overbased detergents. The lubricant contains about 500 ppm of phosphorus.

Example 2 (EX2) is similar to Example 1, except 0.64 wt % of the product of Preparative Example 1 above is employed. The lubricant contains about 500 ppm of phosphorus.

Comparative Example 1 (CE1) is similar to Example 2, except the product of Preparative Example 1 is replaced with a material prepared from PCE1. The lubricant contains about 500 ppm of phosphorus.

Comparative Example 2 (CE2) is similar to Example 1, except the lubricant does not contain the tartrate diester of a C₆ to C₁₅ alcohol. The lubricant contains about 500 ppm of phosphorus.

Comparative Example 3 (CE3) contains (i) 0.59 wt % of the product of PCE1, and (ii) other conventional engine oil additives including antioxidants, viscosity modifiers, succinimide dispersants, glycerol monooleate friction modifiers, foam inhibitors, pour point depressants, and overbased detergents. The lubricant contains about 500 ppm of phosphorus.

Comparative Example 4 (CE4) contains (i) 0.64 wt % of the product of Preparative Example 1 above is employed, and (ii) other conventional engine oil additives including antioxidants, viscosity modifiers, succinimide dispersants, glycerol monooleate friction modifiers, foam inhibitors, pour point depressants, and overbased detergents. The lubricant contains about 500 ppm of phosphorus.

Each of the examples and comparative examples are evaluated for wear using a high frequency reciprocating rig (HFRR). Each sample is treated with 1 wt % cumene hydroperoxide. HFRR conditions for the evaluations are 500 g load, 75 minute duration, 1000 micrometer stroke, 20 hertz frequency, and isothermal temperature profile at 105° C. Wear scar in micrometers and film formation as percent film thickness are then measured with lower wear scar values and higher film formation values indicating improved wear performance.

The percent film thickness is based on the measurement of electrical potential between an upper and a lower metal test plate in the HFRR. When the film thickness is 100%, there is a high electrical potential for the full length of the 1000 micrometre stroke, suggesting no metal to metal contact. Conversely for a film thickness of 0% there is no electrical potential suggesting continual metal to metal contact between the plates. For intermediate film thicknesses, there is an electrical potential suggesting the upper and lower metal test plate have a degree of metal to metal contact as well as other areas with no metal to metal contact. The results obtained are:

Example Wear Scar (μm) Film Thickness (%) EX1 304 36 EX2 159 85 CE1 405 2 CE2 400 3 CE3 388 2 CE4 401 2

Overall the results indicate that the lubricating composition containing both (i) the tartrate ester and (ii) the salt of a sulphur-free phosphorus-containing compound is capable of providing an internal combustion engine with acceptable levels of wear performance and formation of a film.

Comparison of EX1 and EX2 with CE5

Example CE5 is a lubricant composition containing (i) a commercially available zinc dialkyldithiophosphate (ZDDP) known to be employed in an internal combustion engine lubricant, and (ii) other conventional engine oil additives including antioxidants, viscosity modifiers, succinimide dispersants, glycerol monooleate friction modifiers, foam inhibitors, pour point depressants, and overbased detergents. The lubricant contains about 500 ppm of phosphorus. CE5 is evaluated in the HFRR in a similar way as described above. The results obtained for CE5 indicate a wear scar of 260 μm and a film thickness of 29%. Comparing CE5 to EX2 indicates that the invention lubricant (EX2) has reduced wear and increased film thickness relative to a lubricant containing conventional ZDDP. Comparing CE5 to EX1 indicates that the invention lubricant (EX1) has performance approaching commercially available ZDDP containing lubricants. In addition, EX1 has increased film thickness formation relative to CE5.

In summary EX2 has improved performance over CE1 to CE5 in both wear reduction and increased film thickness formation. EX1 is improved over comparative examples CE1 to CE4 in both wear reduction and increased film thickness. Further EX1 is has wear performance approaching that of CE5 without the need to employ ZDDP.

Examples 3 to 4 and Comparative Example 6

Example 3 (EX3) is similar to EX1, except 1 wt % of butyl citrate is used instead of the tartrate diester of a C₆ to C₁₅ alcohol.

Example 4 (EX4) is similar to EX2, except 1 wt % of butyl citrate is used instead of the tartrate diester of a C₆ to C₁₅ alcohol.

Comparative Example 6 (CE6) is similar to CE1, except 1 wt % of butyl citrate is used instead of the tartrate diester of a C₆ to C₁₅ alcohol.

EX3, EX4 and CE6 are evaluated in the HFRR in a similar way as described above. The HFRR wear result obtained for EX3, EX4 and CE6 is 412 μm, 397 μm and 404 μm respectively. The film thickness result obtained for EX3, EX4 and CE6 is 2%, 2% and 3% respectively.

Examples EX5 to EX6 and Comparative Examples CE7

Preparation of Phosphorylated Dispersant 1 (DP1): a flask is charged with a mono-succinimide dispersant (TBN=100, 570 g). The flask is warmed to 120° C. and purged with nitrogen. H₃PO₄ (85%, 39 g) is charged drop-wise over 1 hour. The flask is warmed to 155° C. and stirred vigorously for 5 hours. Diatomaceous earth (25 g) is added and the product is filtered and cooled to yield a brown oil (511 g).

Preparation of Phosphorylated Dispersant 2 (DP2): a flask is charged with mono-succinimide dispersant (TBN=100, 570 g). The material is warmed to 110° C. and purged with nitrogen. Solid H₃PO₃ (27 g) is dissolved in water (27 g) and the solution is added to the preparation drop-wise over 1 hour. The flask is warmed to 155° C. and stirred for 5 hours. Diatomaceous earth (25 g) is added and the product is filtered to yield a dark orange oil (488 g).

Example 5 (EX5) is a 5W-30 lubricant containing (i) 2.8 wt % of the product of DP1, (ii) 1 wt % of a tartrate diester of a C₆ to C₁₅ alcohol, and (iii) other conventional engine oil additives including antioxidants, viscosity modifiers, succinimide dispersants, glycerol monooleate friction modifiers, foam inhibitors, pour point depressants, and overbased detergents. The lubricant contains about 500 ppm of phosphorus.

Example 6 (EX6) is similar to EX5, except 2.3 wt % of the product of DP2 is used instead of DP1. The lubricant contains about 500 ppm of phosphorus.

Comparative Example 7 (CE7) is similar to EX5, except it does not contain 1 wt % of a tartrate diester of a C6 to C15 alcohol.

Examples EX5 to EX6 and comparative example CE7 are evaluated for wear using a high frequency reciprocating rig (HFRR) by the methodology described above. The results obtained are:

Example Wear Scar (μm) Film Thickness (%) EX5 170 49 EX6 174 44 CE7 416 4

Overall the results indicate that a lubricating composition containing both (i) the tartrate ester, and (ii) the phosphorylated dispersant is capable of providing an internal combustion engine with acceptable levels of wear performance and formation of a film.

It is known that some of the materials described above may interact in the final formulation, so that the components of the final formulation may be different from those that are initially added. The products formed thereby, including the products formed upon employing lubricant composition of the present invention in its intended use, may not be susceptible of easy description. Nevertheless, all such modifications and reaction products are included within the scope of the present invention; the present invention encompasses lubricant composition prepared by admixing the components described above.

Each of the documents referred to above is incorporated herein by reference. Except in the Examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as modified by the word “about.” Unless otherwise indicated, each chemical or composition referred to herein should be interpreted as being a commercial grade material which may contain the isomers, by-products, derivatives, and other such materials which are normally understood to be present in the commercial grade. However, the amount of each chemical component is presented inclusive of any solvent or diluent oil, which may be customarily present in the commercial material, unless otherwise indicated. It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention may be used together with ranges or amounts for any of the other elements.

As used herein, the term “hydrocarbyl substituent” or “hydrocarbyl group” is used in its ordinary sense, which is well-known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having predominantly hydrocarbon character. Examples of hydrocarbyl groups include: hydrocarbon substituents, including aliphatic, alicyclic, and aromatic substituents; substituted hydrocarbon substituents, that is, substituents containing non-hydrocarbon groups which, in the context of this invention, do not alter the predominantly hydrocarbon nature of the substituent; and hetero substituents, that is, substituents which similarly have a predominantly hydrocarbon character but contain other than carbon in a ring or chain. A more detailed definition of the term “hydrocarbyl substituent” or “hydrocarbyl group” is described in paragraphs [0118] to [0119] of International Publication WO2008147704.

While the invention has been explained in relation to its preferred embodiments, it is to be understood that various modifications thereof will become apparent to those skilled in the art upon reading the specification. Therefore, it is to be understood that the invention disclosed herein is intended to cover such modifications as fall within the scope of the appended claims. 

1-19. (canceled)
 20. A lubricating composition comprising an oil of lubricating viscosity and an antiwear package, wherein the antiwear package comprises: (a) 0.25 to 2.5 wt % of an antiwear agent represented by a compound of Formula (1a) and/or (1b):

wherein n′ is 0 to 10 for Formula (1b), and 1 to 10 for Formula (1a); p is 1 to 5; Y and Y′ are independently —O—, >NH, >NR³, or an imide group formed by taking together both Y and Y′ groups in (1b) or two Y groups in (1a) and forming a R′—N< group between two >C═O groups; X is independently —CH₂—, >CHR⁴, >CR⁴R⁵, >CHOR⁶, >C(CO₂R⁶)₂, —CH₃, CH₂R⁴, —CHR⁴R⁵, —CH₂OR⁶, —CH(CO₂R⁶)₂, >C(OR₆)CO₂R⁶, >CHCO₂R⁶, or ≡C—R⁶ or mixtures thereof to fulfill the valence of Formula (1a) and/or (1b); R¹ and R² are independently hydrocarbyl groups, containing 1 to 150 carbon atoms; R³ is a hydrocarbyl group; R⁴ and R⁵ are independently keto-containing groups, ester groups or hydrocarbyl groups; and R⁶ is independently hydrogen or a hydrocarbyl group; and (b) 0.25 to 2.5 wt % of a salt of a sulphur-free phosphorus-containing compound.
 21. The lubricating composition of claim 20, wherein sulphur-free phosphorus-containing compound is a phosphorylated dispersant.
 22. The lubricating composition of claim 21, wherein the phosphorylated dispersant is a nitrogen-containing dispersant selected from the group consisting of: (i) hydrocarbyl-substituted succinimides; (ii) mixed ester/amides of hydrocarbyl-substituted succinic acid made using alkanois, amines, and/or aminoalkanols; Mannich dispersants which are condensation products of hydrocarbyl-substituted phenols, formaldehyde and polyethylene polyamines; and (iv) mixtures thereof.
 23. The lubricating composition of claim 22, wherein the nitrogen-containing dispersant is a polyisobutylene succinimide with number average molecular weight of the polyisobutylene substituent in the range 500 to
 3000. 24. The lubricating composition of claim 20, wherein the compound of Formula (1a) and/or (1b) is a derivative of a hydroxycarboxylic acid.
 25. The lubricating composition of claim 20, wherein X is hydroxyl-containing, and the compound Formula (1a) and/or (1b) is derived from hydroxycarboxylic acids selected from the group consisting of tartaric acid, citric acid, and mixtures thereof.
 26. The lubricating composition of claim 20, wherein X is hydroxyl-containing, and the compound Formula (1a) and/or (1b) is derived from tartaric acid.
 27. The lubricating composition of claim 20, wherein the compound Formula (1a) and/or (1b) is an imide, a di-ester, a di-amide, or an ester-amide derivative of tartaric acid.
 28. A method for lubricating an internal combustion engine comprising supplying to the engine a lubricating composition of claim
 20. 29. The method of claim 28, wherein the internal combustion engine is a 2-stroke engine.
 30. The method of claim 28, wherein the internal combustion engine is a 4-stroke engine.
 31. The method of claim 28, wherein the lubricating composition has (i) a sulphur content of 0.5 wt % or less, (ii) a phosphorus content of 0.07 wt % or less, and (iii) a sulphated ash content of 1.5 wt % or less.
 32. The method of claim 28, wherein the lubricating composition has a sulphur content in the range of 0.001 wt % to 0.5 wt %.
 33. The lubricating composition of claim 20, wherein of the salt of a sulphur-free phosphorus-containing compound is represented Formula (2):

wherein A and A′ are independently H, or a hydrocarbyl group containing 1 to 30 carbon atoms; each R and R″ group are independently a hydrocarbyl group; each R′ is independently R, H, or a hydroxyalkyl group; Y is independently R′, or a group represented by RO(R′O)P(O)—CH(A′)CH(A)-; x′ ranges from 0 to 1; and m and n are both positive non-zero integers, with the proviso that the sum of (m+n) is equal to 4; M is a metal ion; t is an integer varying from 1 to 4; and q and e are fractions, whose total provides complete valence to satisfy t, with the proviso that q is in the range of 0.1 to 1.5, and e is in the range of 0 to 0.9.
 34. The lubricating composition of claim 33, wherein the compound of Formula (2) is free of a metal ion (e is equal to zero and q is equal to one).
 35. A method for lubricating an internal combustion engine comprising supplying to the engine a lubricating composition of claim
 33. 36. The method of claim 35, wherein the internal combustion engine is a 2-stroke engine.
 38. The method of claim 35, wherein the internal combustion engine is a 4-stroke engine.
 38. The method of claim 35, wherein the lubricating composition has (i) a sulphur content of 0.5 wt % or less, (ii) a phosphorus content of 0.07 wt % or less, and (iii) a sulphated ash content of 1.5 wt % or less.
 39. The method of claim 35, wherein the lubricating composition has a sulphur content in the range of 0.001 wt % to 0.5 wt %. 